The objective of this project is to expand our knowledge of the absorptive function of the trachea and conducting airways. It is a topic about which very little is known at present. We will instill radiolabeled drugs and proteins into the trachea of hamsters and rabbits and determine by scintillation spectrometry and light and electron microscope autoradiography the rate and route of their absorption into the blood. We will study the novel idea developed from our preliminary experiments that a pathway for very rapid protein uptake may exist in the lung. In other studies, employing a unique in vivo rabbit model, we will attempt to quantify the extent to which the trachea functions in the absorption of drugs and proteins as a fraction of total absorption below the larynx. We will also explore the effect of mucus hypersecretion on the rate of drug and protein absorption using elastase-treated hamsters. In addition to yielding valuable information about the absorptive clearance function of airways, these studies may have potential clinical significance for the use of aerosol therapy in disease of the lung or other organs.